Depend on what you order.
Have a look at data sheet (from the same webpage, a bit lower:
http://www.usdigital.com/assets/gene...atasheet_4.pdf)
2500 CPR will give you (with Ek box or equivalent) resolution of 10000 ticks per rev (because it uses both channels for counting, and also it counts rising and falling edges of individual pulses- that is why the res is 4X).